It is more than a 95% chance that you will have problems if you do not proceed as descibed below:
Repair Install to SET XP to New Motherboard
1. Do Not BOOT into Windows XP on first boot after Motherboard or Hard Drive change! If booting from CD is not an option, return to BIOS and make sure booting from CD is the first boot option. Booting into Windows is only an option when you do a direct replacement of the Motherboard, ie replace failed board with exactly the same one.
2.If your computer does not support booting from the CD, check your OEM or Motherboard makers web site for updated BIOS.
3.Perform a Repair Install by following the step by step below.
When you see the "Welcome To Setup" screen, you will see the options below
This portion of the Setup program prepares Microsoft
Windows XP to run on your computer:
To setup Windows XP now, press ENTER.
To repair a Windows XP installation using Recovery Console, press R.
To quit Setup without installing Windows XP, press F3.
Press Enter to start the Windows Setup.
Accept the License Agreement and Windows will search for existing Windows installations.
Select the XP installation you want to repair from the list and press R to start the repair.
Setup will copy the necessary files to the hard drive and reboot. Do not press any key to boot from CD when the message appears. Setup will continue as if it were doing a clean install, but your applications and settings will remain intact.